1. Field of the Invention
The present invention relates to a signal sequence peptide for the improvement of extracellular secretion efficiency of a heterologous protein in E. coli. 
2. Description of the Related Art
As the protein related industry becomes bigger, recombinant proteins are being produced in different expression systems according to the purpose of use and the scale of production. The expression systems are classified by a biological host, and the most representative expression systems are the ones using microorganisms such as E. coli or yeast, insect cells, animal cells, and plant cells, etc. In particular, E. coli expression system is most widely used because it is easy for gene manipulation and economical. However, it has disadvantages for the production of eukaryote-originated proteins such as cytokine because post-translational modification such as glycosylation is not possible in there and protein secretion in a culture medium is difficult. In addition, most proteins are produced as inactive insoluble forms such as inclusion body because of unsatisfactory level of folding of disulfide bond. There have been attempts to overcome these problems by thorough studies of secretion expression, co-expression of molecular chaperon, and re-folding, etc.
The present inventors tried to confirm what elements could improve the efficiency of protein secretion. As a result, the present inventors confirmed that the polypeptide comprising 23 amino acid residues (SEQ. ID. NO. 3) at N-terminal of beta-agarase AgaB34 (Gene Bank Accession NO. EU200967; nts SEQ. ID. NO. 1, aa SEQ. ID. NO. 2) could be used as a signal sequence peptide for the improvement of secretion efficiency of a heterologous protein in E. coli, leading to the completion of the present invention.